In U.S. Pat. No. 3,636,952, issued Jan. 25, 1972, which is owned by the same assignee as the present invention, there is disclosed a disposable diaper consisting essentially of paper and comprising a special water permeable cellulosic top layer for contact with the baby's skin, a waterproof thin plastic bottom layer and an intermediate moisture absorbent pad containing several layers of paper wadding and a layer of fiberized pulp having high moisture absorbent properties.
The above-mentioned top layer, which is made of a special form of cellulosic fibers, and the fiberized pulp layer, which has a superior high loft, softness and freedom from knots and dust, have contributed substantially to the commercial success of the disposable diaper. This special top layer component is covered by U.S. Pat. No. 3,171,773, issued Mar. 2, 1965. And the superior fiberized pulp component is covered by U.S. Pat. Nos. RE26,939, issued Aug. 18, 1970, 3,554,862, issued Jan. 12, 1971 and 3,554,863, issued Jan. 12, 1971. All of these patents are assigned to the same assignee as the present application and identify an extensive line of research and development in the disposable diaper field.
The commercial diaper product disclosed in said U.S. Pat. No. 3,636,952, issued Jan. 25, 1972, has been the subject of further research and has been markedly improved in accordance with the present invention. Two important features are (a) combining of the top and bottom sheets along the transverse edges of the disposable diaper in a secure yet soft and comfortable manner, and (b) an arrangement for maintaining the fiberized pulp layer in a permanent stable position in the disposable diaper. The prior problems and their solution by the present invention are identified somewhat more in detail as follows: